1. Field of the Invention
The present invention relates to the improvement of a pivoting display device that comprise a video monitor that is used over the head of a passengers especially in aircraft and that can pivot the monitor open from its stowage position to its display position.
2. Description of the Background Art
Many passenger aircraft are provided with video monitors for every 2-3 rows of passenger seats to show and play movies, information about the flight and other similar material to passengers. These monitors are usually fixed to Passenger Service Unit (PSU) rails attached under the overhead baggage rack/compartment above the passenger seat. Said monitors are attached so that they can be swung open downwards to the display position and can be stowed back after their use. These devices are also provided with an electric motor and a drive mechanism that conveys the motor's rotating force. It is desirable that this pivoting display device can retract its monitor into the stowage position in case the power supply to the cabin fails for some reason.
The Federal Aviation Administration (FAA) requires that all monitors to be stowed into their stowing location to secure the safety of passengers in case the power supply to the cabin fails.
Several prior art pivoting display devices have been disclosed, for example, in U.S. Pat. No. 5,096,271 (Portman, Mar. 17, 1992) and U.S. Pat. No. 5,467,106 (Salomon, Nov. 14, 1995), display devices are configured to retract the monitor to the stowage position using a spring mechanism in case the power supply fails. For those using the spring mechanism, the spring usually contracts when the monitor is driven to the display position thus the energy accumulated in the spring is used as a driving force to stow the monitor. The driving mechanism that conveys the rotating force of the motor and that consists of a gear transmission mechanism or a link mechanism etc. is arranged between the motor and the monitor and conveys the swinging force to pivot the monitor.
Other pivoting display devices are, as disclosed for instance in U.S. Pat. No. 6,373,216 (Ho, Apr. 16, 2002), configured to use the forward and reverse rotation of the motor to open and close the monitor instead of using a spring mechanism when stowing the monitor. This device uses capacitors as a power unit to reverse rotate the motor in the direction of stowing the monitor. That is, it charges the capacitor while the power is supplied and the monitor is in its opened state and then drives the monitor in the direction of stowing it by changing over the circuit with a relay and by reverse rotating the motor using the power charged in the capacitor.
Systems wherein stowage of the monitor in case of a power failure is by using a spring mechanism need to accumulate a decompression force in the spring when driving the monitor to its open position. The motor used for this therefore carries a heavy load, thus necessitating the use of a motor with a capacity enough to carry this load. Their operational reliability when driven by the motor is also prone to problems. The spring mechanism provides a force urging stowing the monitor while the monitor is in its opened state since it needs to rotate and stow the monitor by itself in case of a power failure. When this occurs, the motor and gear box have to disconnect from the spring mechanism which may require a clutch, thereby further complicating the mechanism. The monitor needs to be braked or locked by an urging force larger than the urging force of the spring mechanism in the direction of stowing the monitor so as to maintain its opened state against the force urging stowage. Furthermore, a mechanical type device using the spring mechanism to stow the monitor, especially the spring mechanism carrying said constant load is prone to deterioration by a secular change which results in problems in maintaining its reliability.